JP2017168213A - Resin microparticle for power storage device, power storage device electrode, and power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: resin microparticles for a power storage device, which make possible to provide a power storage device superior in adhesion with a current collector and an active material, and superior in charge and discharge cycle characteristics; a power storage device electrode including the resin microparticles; and a power storage device including the electrode.SOLUTION: The above problem is solved by a resin microparticle for a power storage device electrode, which comprises: a unit of a monomer (a) having, as a constituting unit of the resin microparticle, at least one functional group selected from a group consisting of a hydroxy group and an amide group; a unit of a cross-linkable monomer (b); and a unit of a monomer (c) other than the monomers (a) and (b). To all of the monomers constituting the resin microparticle, the unit of the monomer (a) is over 20 mass% up to 50 mass%, the unit of the cross-linkable monomer (b) is 0.1 to 10 mass%, and the unit of the monomer (c) is 40 mass% or more and less than 79.9 mass%.SELECTED DRAWING: None

Description

The present invention relates to resin fine particles for power storage devices, a power storage device electrode obtained using the resin fine particles, and a power storage device.

In recent years, small portable electronic devices such as digital cameras and mobile phones have been widely used. These electronic devices have always been required to minimize the volume and reduce the mass, and the batteries to be mounted are also required to be small, light, and have a large capacity. Also, in large-sized secondary batteries for automobiles and the like, it is desired to realize a large-sized secondary battery instead of the conventional lead-acid battery, and there is a need for a longer life in various environments where the battery is used. It has been. In addition, capacitors such as electric double layer capacitors and lithium ion capacitors are also attracting attention as power storage devices with high output and high energy density.

In order to meet such demands, there is an increasing interest in developing power storage devices such as secondary batteries such as lithium ion secondary batteries and alkaline secondary batteries and capacitors, for example, the development of binders for electrodes.

In addition to the electrode active material, the electrode of the electricity storage device requires a binder that binds it to the current collector. Among power storage devices, in particular, fluorine resins such as polyvinylidene fluoride and polytetrafluoroethylene have been conventionally used for binder resins for secondary batteries, both for positive and negative electrodes (Non-Patent Documents 1 and 2). However, in the secondary battery, since the positive electrode or the negative electrode repeats volume expansion and contraction during charge and discharge, the active material and the conductive agent may be dropped, thereby shortening the charge / discharge cycle life. Therefore, the electrode binder is required to have a cushioning property that can withstand the swelling and shrinkage of the electrode. However, the fluororesin has insufficient cushioning ability to follow the electrode. Moreover, the adhesiveness (henceforth adhesiveness) to a collector or an active material is also bad, and if a binder resin is not used in large quantities, the effect as a binder will not be expressed. For this reason, the active material density in the electrode cannot be increased, which has been an obstacle to producing a high-capacity battery electrode. In addition, the fluororesin has a feature that it dissolves only in a specific solvent such as N-methylpyrrolidone, and there is a problem of adverse effects on the human body and the environment, such as an unpleasant odor during electrode fabrication.

In response to these problems, development of resin particles in an aqueous dispersion as an electrode binder has been underway. Patent Document 1 reports a resin incorporating an acidic functional group, a nitrile group, or a crosslinking group, and discloses that the resin has excellent cycle characteristics and adhesion. Patent Document 2 reports an aqueous dispersion of a resin incorporating an acidic functional group, a nitrile group, or a crosslinking group, and discloses that the resin has excellent cycle characteristics and adhesion. An aqueous dispersion of a resin incorporating a perfluoroalkyl group has been reported, and it has been reported that an electrode excellent in bendability and battery characteristics can be obtained. As described above, various functional groups have been introduced and composition optimization has been promoted in the development of aqueous dispersion resin fine particles. However, as the demand for power storage devices continues to increase, further electrode adhesion There is also a need for improved charge / discharge cycle characteristics.

In contrast to the development of such water-dispersed resin fine particles, the use of water-soluble resins as binders is being studied. Patent Document 3 reports a water-soluble binder having a carboxylic acid group which is a polar functional group having excellent adhesion to an active material and a current collector. However, such water-soluble resins with many polar functional groups have the property of greatly changing the viscosity of the aqueous solution due to the change in liquidity, and it is difficult to handle with a slurry for electrode preparation that contains various components. There is a disadvantage of becoming.

“Battery Handbook” published by Denki Shoin 1980 "Industrial Materials" September 2008 (Vol.56, No.9)

International Patent Publication WO2011 / 002057 JP 2002-042819 A JP2013-033692A

An object of the present invention is to provide resin particles for an electricity storage device that can provide an electricity storage device having excellent adhesion to a current collector and an active material and having excellent charge / discharge cycle characteristics. Furthermore, it aims at providing the electrical storage device electrode using this resin fine particle, and the electrical storage device using this electrode.

According to a first aspect of the present invention, as a constituent unit of resin fine particles, a monomer (a) unit having at least one functional group selected from the group consisting of a hydroxy group and an amide group, a crosslinkable monomer (b) unit, The monomer (a) and the monomer (c) unit other than the monomer (b), and the monomer (a) unit exceeds 20% by mass and is 50% by mass or less with respect to all monomers constituting the resin fine particles. The present invention relates to a resin fine particle for an electricity storage device electrode, wherein the monomer (b) unit is 0.1% by mass or more and 10% by mass or less, and the monomer (c) unit is 40% by mass or more and less than 79.9% by mass.

Moreover, 2nd invention is related with the resin fine particle for electrical storage device electrodes of 1st invention characterized by the swelling rate in electrolyte solution immersion being 200% or more.

The third invention relates to the resin fine particles for an electricity storage device electrode of the first or second invention, wherein the resin fine particles have a glass transition temperature of −60 to 60 ° C.

Moreover, 4th invention is related with the resin fine particle for electrical storage device electrodes of any one of 1st-3rd invention characterized by the average particle diameter of the said resin fine particle being 50-500 nm.

Moreover, 5th invention is 40 to 79.9 mass% of C1-C4 alkyl (meth) acrylate monomers (d) as a monomer (c) with respect to all the monomers which comprise resin fine particles. The present invention relates to a resin fine particle for an electricity storage device electrode according to any one of the first to fourth inventions, characterized by comprising

Moreover, 6th invention is related with the electrical storage device electrode characterized by using the resin fine particle for electrical storage device electrodes of any one of 1st-5th invention.

The seventh invention relates to an electricity storage device comprising a positive electrode, a negative electrode, and an electrolytic solution, wherein at least one of the positive electrode or the negative electrode is the electricity storage device electrode of the sixth invention.

The resin fine particles for an electricity storage device of the present invention are excellent in adhesion to a current collector and an active material, and by using the resin fine particles, an electrode excellent in adhesion to the current collector can be provided, and thus excellent. It is possible to provide an electricity storage device having charge / discharge cycle characteristics.

The resin particle for an electricity storage device of the present invention is obtained by copolymerizing a monomer having at least one functional group selected from the group consisting of a hydroxy group and an amide group. Adhesion can be improved when at least one functional group selected from the group consisting of a hydroxy group and an amide group in the resin fine particles exhibits good adhesion to the current collector and the active material.

<Resin fine particles>
The resin fine particles for an electricity storage device electrode of the present invention include a monomer (a) unit having at least one functional group selected from the group consisting of a hydroxy group and an amide group as a constituent unit of the resin fine particle, and a crosslinkable monomer (b) unit. And monomer (a) and monomer (c) units other than monomer (b),
The monomer (a) unit exceeds 20% by mass and is 50% by mass or less, the crosslinkable monomer (b) unit is 0.1% by mass to 10% by mass, and the monomer (c) ) The unit is 40% by mass or more and less than 79.9% by mass.

The monomer (a), the crosslinkable monomer (b), the monomer (a), and the monomer (c) other than the monomer (b), which are raw materials for each monomer unit constituting the resin fine particles, will be described.

<Monomer (a)>
The monomer (a) is a monomer having at least one functional group selected from the group consisting of a hydroxy group and an amide group. By using the monomer (a), a hydroxy group or an amide group can be left in or on the surface of the resin fine particles, whereby physical properties such as adhesion can be improved.

Examples of the monomer having a hydroxy group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2- (meth) acryloyloxyethyl-2-hydroxy. Ethylphthalic acid, glycerol mono (meth) acrylate, 4-hydroxyvinylbenzene, (meth) allyl alcohol, 3-buten-1-ol, 5-hexen-1-ol, polyethylene glycol (meth) acrylate, polypropylene glycol (meta ) Acrylate, polytetramethylene glycol (meth) acrylate, hexaethylene glycol (meth) acrylate, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, diethylene glycol Vinyl ether, 4-hydroxybutyl vinyl ether, eugenol, etc. isoeugenol and the like.

Examples of the monomer having an amide group include (meth) acrylamide, N-methylolacrylamide, N, N-di (methylol) acrylamide, N-methylol-N-methoxymethyl (meth) acrylamide, and N-methoxymethyl- (meta). ) Acrylamide, N-ethoxymethyl- (meth) acrylamide, N-propoxymethyl- (meth) acrylamide, N-butoxymethyl- (meth) acrylamide, N-pentoxymethyl- (meth) acrylamide, N, N-di ( Methoxymethyl) acrylamide, N-ethoxymethyl-N-methoxymethylmethacrylamide, N, N-di (ethoxymethyl) acrylamide, N-ethoxymethyl-N-propoxymethylmethacrylamide, N, N-di (propoxymethyl) acrylic Ami N-butoxymethyl-N- (propoxymethyl) methacrylamide, N, N-di (butoxymethyl) acrylamide, N-butoxymethyl-N- (methoxymethyl) methacrylamide, N, N-di (pentoxymethyl) Acrylamide, N-methoxymethyl-N- (pentoxymethyl) methacrylamide, N, N-dimethylaminopropylacrylamide, N, N-diethylaminopropylacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, diacetone And (meth) acrylamide.
From the viewpoint of improving adhesion, it is preferable to use a monomer having a primary amide group or a secondary amide group having active hydrogen.

Examples of the monomer having both a hydroxy group and an amide group include N-hydroxyethylacrylamide, N-hydroxymethylacrylamide, N- (2-hydroxyphenyl) acrylamide, and the like.

In the present invention, the monomer (a) is more than 20 and less than 50% by mass, preferably more than 20 and less than 30% by mass with respect to the total monomers. If it exceeds 20 and is less than 50% by mass, the effect of improving the adhesion to the current collector and the active material is great, and excellent adhesion and charge / discharge cycle characteristics can be obtained. Further, the resin fine particles have an appropriate polarity, and are excellent in stability as resin fine particles.

<Crosslinkable monomer (b)>
The crosslinkable monomer (b) is a monomer having two or more ethylenically unsaturated bonds or a monomer having an ethylenically unsaturated bond and an alkoxysilyl group. By using the crosslinkable monomer (b), the resin fine particle inside and between the particles and the current collector have a cross-linked structure, improving the dispersibility in water, resistance to the electrolyte, and adhesion to the current collector. Thus, the cycle characteristics of the electricity storage device can be improved.

Examples of the monomer having two or more ethylenically unsaturated bonds include allyl (meth) acrylate, 1-methylallyl (meth) acrylate, 2-methylallyl (meth) acrylate, 1-butenyl (meth) acrylate, (Meth) acrylic acid 2-butenyl, (meth) acrylic acid 3-butenyl, (meth) acrylic acid 1,3-methyl-3-butenyl, (meth) acrylic acid 2-chloroallyl, (meth) acrylic acid 3-chloroallyl , O-allylphenyl (meth) acrylate, 2- (allyloxy) ethyl (meth) acrylate, allyl lactyl (meth) acrylate, citronellyl (meth) acrylate, geranyl (meth) acrylate, rosinyl (meth) acrylate , Cinnamyl (meth) acrylate, diallyl maleate, diallyl itaconic acid, (meth) acrylic acid Vinyl acid, vinyl crotonate, vinyl oleate, vinyl linolenate, 2- (2′-vinyloxyethoxy) ethyl (meth) acrylate, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, Di (meth) acrylate triethylene glycol, di (meth) acrylate tetraethylene glycol, tri (meth) acrylate trimethylolpropane, tri (meth) acrylate pentaerythritol, 1,1,1-trishydroxymethyl diacrylate Ethane, 1,1,1-trishydroxymethyl ethane triacrylate, 1,1,1-trishydroxymethylpropane triacrylic acid, divinylbenzene, divinyl adipate, diallyl isophthalate, diallyl phthalate, diallyl maleate, etc. can give

Examples of the monomer having an ethylenically unsaturated bond and an alkoxysilyl group include γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltributoxysilane, and γ-methacryloxy. Propylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-acryloxypropylmethyldimethoxysilane, γ-methacryloxymethyltrimethoxysilane , Γ-acryloxymethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, vinylmethyldimethoxysilane and the like.

In this invention, a crosslinking | crosslinked monomer (b) is 0.1 to 10 mass% with respect to all the monomers, Preferably it is 1 to 5 mass%. When the content is 0.1% by mass or more and 10% by mass or less, crosslinking in the resin fine particles becomes a preferable density, and both resistance to the electrolyte and flexibility of the resin can be achieved, and excellent cycle characteristics and adhesion can be obtained. .

<Monomer (c)>
The resin fine particles of the present invention can be obtained by simultaneously polymerizing a monomer (c) other than the monomer (a) and the crosslinkable monomer (b) in addition to the monomer (a) and the crosslinkable monomer (b).

In this invention, a monomer (c) is contained 40 mass% or more and less than 79.9 mass% with respect to all the monomers.

The monomer (c) is not particularly limited as long as it is copolymerizable except for the monomer (a) and the crosslinkable monomer (b), but the alkyl (meth) acrylate monomer (d) having 1 to 4 carbon atoms. It is preferable to contain. The content of the (meth) acrylate monomer (d) is not particularly limited, but when it is contained in an amount of 40% by mass or more and less than 79.9% by mass with respect to all monomers constituting the resin fine particles, This is preferable because of excellent adhesion.

Examples of the alkyl (meth) acrylate monomer (d) having 1 to 4 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n- Examples include butyl (meth) acrylate, i-butyl (meth) acrylate, and t-butyl (meth) acrylate.

Examples of the monomer (c) include n-amyl (meth) acrylate, i-amyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. , Nonyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, myristyl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, n-tetradecyl (meth) acrylate, etc. The above alkyl (meth) acrylate monomer is mentioned.

Examples of the monomer (c) include cyclic alkyl (meth) acrylate monomers such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate.

Examples of the monomer (c) include monomers having an aromatic ring such as benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, styrene, α-methylstyrene, 2-methylstyrene, chlorostyrene, and allylbenzene. It is done.

Examples of the monomer (c) include vinyl monomers having a heterocyclic ring such as N-vinylpyrrolidone, vinylpyridine, and vinylimidazole.

Examples of the monomer (c) include vinyl ether monomers such as butyl vinyl ether and ethyl vinyl ether.

Examples of the monomer (c) include acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, isocrotonic acid, α-acetoxyacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, and phthalic acid β- ( (Meth) acryloxyethyl monoester, isophthalic acid β- (meth) acryloxyethyl monoester, terephthalic acid β- (meth) acryloxyethyl monoester, succinic acid β- (meth) acryloxyethyl monoester, methylmaleic acid , Dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, vinylsulfonic acid, methylvinylsulfonic acid, (meth) allylsulfonic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfone Acid, 3-allyloxy-2-hydride Acidic monomers such as loxypropanesulfonic acid, phosphoric acid-2- (meth) acryloyloxyethyl phosphate, methyl-2- (meth) acryloyloxyethyl phosphate, ethyl phosphate- (meth) acryloyloxyethyl, etc. And monomers having a group.

Examples of the monomer (c) include n-butoxypolyethylene glycol (meth) acrylate, n-pentoxypolyethylene glycol (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate, and ethoxypolypropylene. Glycol (meth) acrylate, propoxypolypropylene glycol (meth) acrylate, n-butoxypolypropylene glycol (meth) acrylate, n-pentoxypolypropylene glycol (meth) acrylate, phenoxypolypropylene glycol (meth) acrylate, methoxypolytetramethylene glycol (meta ) Acrylate, phenoxytetraethylene glycol (meth) acrylate, methoxy Such as hexa ethylene glycol (meth) acrylate, a monomer having a polyalkylene glycol ether in the molecule.

Examples of the monomer (c) include monomers having a nitrile group such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile.

Examples of the monomer (c) include monomers having a quaternary ammonium base such as dimethylaminoethylmethyl chloride (meth) acrylate.

Examples of the monomer (c) include acrolein, N-vinylformamide, vinyl methyl ketone, vinyl ethyl ketone, acetoacetoxyethyl (meth) acrylate, acetoacetoxypropyl (meth) acrylate, acetoacetoxybutyl (meth) acrylate, and the like. And a monomer having a keto group.

Examples of the monomer (c) include vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, o-allylphenyl glycidyl ether, butadiene monoepoxide, chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3 , 4-epoxy-1-vinylcyclohexene, 1,2-epoxy-5,9-cyclododecadiene, 3,4-epoxy-1-butene, 1,2-epoxy-5-hexene, 1,2-epoxy- 9-decene, glycidyl (meth) acrylate, glycidyl crotonate, glycidyl-4-heptenoate, glycidyl sorbate, glycidyl linoleate, glycidyl-4-methyl-3-pentenoate, glycidyl ester of 3-cyclohexenecarboxylic acid, 4-methyl -3- Monomers having an epoxy group such as glycidyl ester of cyclohexene carboxylic acid.

Examples of the monomer (c) include 3-((meth) acryloyloxymethyl) oxetane, 3-((meth) acryloyloxymethyl) -2-trifluoromethyloxetane, and 3-((meth) acryloyloxymethyl). ) -2-phenyloxetane, 2-((meth) acryloyloxymethyl) oxetane, 2-((meth) acryloyloxymethyl) -4-trifluoromethyloxetane and other monomers having an oxetanyl group.

Examples of the monomer (c) include perfluoromethylmethyl (meth) acrylate, perfluoroethylmethyl (meth) acrylate, 2-perfluorobutylethyl (meth) acrylate, and 2-perfluorohexylethyl (meth) acrylate. 2-perfluorooctylethyl (meth) acrylate, 2-perfluoroisononylethyl (meth) acrylate, 2-perfluorononylethyl (meth) acrylate, 2-perfluorodecylethyl (meth) acrylate, perfluoropropylpropyl Perfluoroalkyl groups such as (meth) acrylate, perfluorooctylpropyl (meth) acrylate, perfluorooctyl amyl (meth) acrylate, perfluorooctyl undecyl (meth) acrylate, etc. Monomers, and the like.

Examples of the monomer (c) include 2- (0- [1′-methylpropylideneamino] carboxyamino) ethyl (meth) acrylate and 2-[(3,5-dimethylpyrazolyl) carbonylamino] ethyl. Examples thereof include monomers having a blocked isocyanate group such as (meth) acrylate and 2- (2- (meth) acryloyloxyethylcarbamoyl) malonate.

These monomers can be used in combination of two or more kinds of monomers in order to adjust the polymerization stability of the particles, the glass transition temperature, and the film formability and film properties.

<Method for producing resin fine particles>
The resin fine particles of the present invention can be synthesized by a conventionally known emulsion polymerization method.

<Emulsifier used in emulsion polymerization>
As the emulsifier used in the emulsion polymerization in the present invention, a conventionally known one such as a reactive emulsifier having an ethylenically unsaturated group or a non-reactive emulsifier having no ethylenically unsaturated group may be arbitrarily used. it can.

Reactive emulsifiers having an ethylenically unsaturated group can be further roughly classified into anionic and nonionic nonionic ones. In particular, an anionic reactive emulsifier or nonionic reactive emulsifier having an ethylenically unsaturated group is preferable, and since the dispersed particle size of the copolymer becomes fine and the particle size distribution becomes narrow, when used as a binder for an electricity storage device. Electrolytic solution resistance can be improved. These anionic reactive emulsifiers or nonionic reactive emulsifiers having an ethylenically unsaturated group may be used singly or in combination.

Although it does not specifically limit as an anionic reactive emulsifier which has an ethylenically unsaturated group, Specifically, alkyl ether type (For example, Dairon Kogyo Seiyaku Co., Ltd. product Aqualon KH-05, KH-10 is used. , KH-20, Adeka Soap SR-10N, SR-20N manufactured by ADEKA Corporation, Latemu PD-104 manufactured by Kao Corporation, etc .; Sulfosuccinic acid ester-based (commercially available products include Latemul S-made by Kao Corporation, for example) 120, S-120A, S-180P, S-180A, Sanyo Chemical Co., Ltd. Eleminol JS-2, etc.); alkyl phenyl ether type or alkyl phenyl ester type (commercially available products include, for example, Daiichi Kogyo Seiyaku Co., Ltd. Aqualon H-2855A, H-3855B, H-3855C, H-3856, HS-0 HS-10, HS-20, HS-30, Adeka Soap SDX-222, SDX-223, SDX-232, SDX-233, SDX-259, SE-10N, SE-20N, etc. manufactured by ADEKA Corporation) ; (Meth) acrylate sulfate ester (commercially available products such as Antox MS-60, MS-2N, Sanyo Kasei Kogyo Co., Ltd. Elminol RS-30, etc., manufactured by Nippon Emulsifier Co., Ltd.); Phosphate ester (commercially available) Examples of the product include H-3330PL manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Adeka Soap PP-70 manufactured by ADEKA Corporation, and the like.

Although it does not specifically limit as a nonionic reactive emulsifier which has an ethylenically unsaturated group, Specifically, for example, an alkyl ether type (As a commercial item, for example, Adeka Soap ER-10, ER-20 by ADEKA Corporation) , ER-30, ER-40, LATEMUL PD-420, PD-430, PD-450, etc. manufactured by Kao Corporation; alkylphenyl ethers or alkylphenyl esters (commercially available products include, for example, Daiichi Kogyo Seiyaku Co., Ltd.) (Aqualon RN-10, RN-20, RN-30, RN-50 manufactured by company, Adeka Soap NE-10, NE-20, NE-30, NE-40 manufactured by ADEKA Co., Ltd.); (meth) acrylate sulfate System (commercially available products include, for example, RMA-564, RMA-568, RMA- manufactured by Nippon Emulsifier Co., Ltd. 114, etc.) and the like.

When the resin fine particles of the present invention are obtained by emulsion polymerization, a non-reactive emulsifier having no ethylenically unsaturated group can be used in combination with the above-described reactive emulsifier having an ethylenically unsaturated group, if necessary. Non-reactive emulsifiers can be broadly classified into non-reactive anionic emulsifiers and non-reactive nonionic emulsifiers.

Examples of non-reactive nonionic emulsifiers include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; polyoxyethylene alkyl such as polyoxyethylene octyl phenyl ether and polyoxyethylene nonyl phenyl ether Sorbitan monolaurate, sorbitan monostearate, sorbitan higher fatty acid esters such as sorbitan trioleate; polyoxyethylene sorbitan higher fatty acid esters such as polyoxyethylene sorbitan monolaurate; polyoxyethylene monolaurate, Polyoxyethylene higher fatty acid esters such as polyoxyethylene monostearate; oleic acid monoglyceride, stearic acid monoglyceride Glycerine higher fatty acid esters such as chloride, polyoxyethylene-polyoxypropylene block copolymers, and the like can be exemplified polyoxyethylene distyrenated phenyl ether.

Examples of non-reactive anionic emulsifiers include higher fatty acid salts such as sodium oleate; alkyl aryl sulfonates such as sodium dodecylbenzene sulfonate; alkyl sulfate esters such as sodium lauryl sulfate; polyoxyethylene lauryl ether Polyoxyethylene alkyl ether sulfates such as sodium sulfate; polyoxyethylene alkylaryl ether sulfates such as polyoxyethylene nonylphenyl ether sodium sulfate; sodium monooctyl sulfosuccinate, sodium dioctyl sulfosuccinate, polyoxyethylene lauryl sulfosuccinic acid Alkylsulfosuccinic acid ester salts such as sodium and derivatives thereof; polyoxyethylene distyrenated phenyl ether And the like can be exemplified sulfuric ester salts.

The usage-amount of the emulsifier used in this invention is not necessarily limited, According to the physical property calculated | required when resin fine particles are finally used as a binder for electrical storage devices, it can select suitably. For example, the emulsifier is usually preferably 0.5 to 40% by mass, more preferably 0.5 to 20% by mass, based on the stability during polymerization, with respect to all monomers constituting the resin fine particles. Preferably, it is in the range of 0.5 to 10% by mass.

In emulsion polymerization of the resin fine particles of the present invention, a water-soluble protective colloid can be used in combination. Examples of the water-soluble protective colloid include, for example, acrylic polymers, styrene acrylic polymers, styrene maleic acid copolymers, partially saponified polyvinyl alcohols, fully saponified polyvinyl alcohols, polyvinyl alcohols such as modified polyvinyl alcohols; hydroxyethyl cellulose, hydroxypropyl cellulose , Cellulose derivatives such as carboxymethyl cellulose salt; natural polysaccharides such as guar gum and the like, and these can be used alone or in a combination of plural kinds. The amount of the water-soluble protective colloid used is 0.1 to 10.0% by mass, more preferably 0.5 to 5% by mass, based on the total monomers constituting the resin fine particles, for reasons of stability during polymerization. %.

<Aqueous medium used in emulsion polymerization>
The aqueous medium used in the emulsion polymerization of the resin fine particles of the present invention includes water, and a hydrophilic organic solvent can be used as long as the object of the present invention is not impaired.

<Polymerization initiator used in emulsion polymerization>
The polymerization initiator used for obtaining the resin fine particles of the present invention is not particularly limited as long as it has the ability to initiate radical polymerization, and a known oil-soluble polymerization initiator or water-soluble polymerization initiator should be used. Can do.

The oil-soluble polymerization initiator is not particularly limited, and examples thereof include benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl hydroperoxide, tert-butyl peroxy (2-ethylhexanoate), and tert-butyl peroxide. Organic peroxides such as oxy-3,5,5-trimethylhexanoate, di-tert-butyl peroxide; 2,2′-azobisisobutyronitrile, 2,2′-azobis-2,4- Examples thereof include azobis compounds such as dimethylvaleronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 1,1′-azobiscyclohexane-1-carbonitrile. These can be used alone or in combination of two or more. Although the usage-amount of these polymerization initiators is not necessarily limited, It is preferable to use the quantity of 0.1-10.0 mass% with respect to all the monomers which comprise resin microparticles | fine-particles.

In the present invention, it is preferable to use a water-soluble polymerization initiator. For example, ammonium persulfate, potassium persulfate, hydrogen peroxide, 2,2′-azobis (2-methylpropionamidine) dihydrochloride and the like are conventionally known. A thing can be used conveniently. Moreover, when performing emulsion polymerization, a reducing agent can be used together with a polymerization initiator if desired. Thereby, it becomes easy to accelerate the emulsion polymerization rate or to perform the emulsion polymerization at a low temperature. Examples of such a reducing agent include reducing organic compounds such as metal salts such as ascorbic acid, ersorbic acid, tartaric acid, citric acid, glucose, and formaldehyde sulfoxylate, sodium thiosulfate, sodium sulfite, sodium bisulfite, Examples include reducing inorganic compounds such as sodium bisulfite, ferrous chloride, Rongalite, thiourea dioxide, and the like. Although the usage-amount of these reducing agents is not necessarily limited, It is preferable to use the quantity of 0.05-5.0 mass% with respect to all the monomers which comprise resin fine particles.

<Conditions for emulsion polymerization>
In addition, it can superpose | polymerize by a photochemical reaction, radiation irradiation, etc. irrespective of an above described polymerization initiator. The polymerization temperature is not less than the polymerization start temperature of each polymerization initiator. For example, in the case of a peroxide-based polymerization initiator, it may be usually about 70 ° C. The polymerization time is not particularly limited, but is usually 2 to 24 hours.

<Other materials used for reaction>
Further, if necessary, sodium acetate, sodium citrate, sodium bicarbonate and the like as a buffering agent, and octyl mercaptan, 2-ethylhexyl thioglycolate, octyl thioglycolate, stearyl mercaptan, lauryl mercaptan as a chain transfer agent A suitable amount of mercaptans such as t-dodecyl mercaptan can be used.

When a monomer having an acidic functional group such as a carboxyl group-containing monomer is used for polymerization of resin fine particles, it can be neutralized with a basic compound before polymerization or after polymerization. Examples of the basic compound include ammonia or alkylamines such as trimethylamine, triethylamine and butylamine; alcohol amines such as 2-dimethylaminoethanol, diethanolamine, triethanolamine and aminomethylpropanol; morpholine. Highly volatile bases such as aminomethyl propanol and ammonia are preferred because they have a high effect of increasing the drying property.

<Characteristics of resin fine particles>
<Swelling rate>
Swelling rate refers to a test piece (hereinafter also referred to as a pre-immersion test piece) obtained by forming resin fine particles into an organic solvent (herein, organic solvent means methanol, ethanol, ethyl acetate, methyl ethyl ketone, toluene, cyclohexane, etc.) Of organic solvents attached to the resin surface after immersion for a certain period of time in a generally used solvent or a solvent used as a secondary battery electrolyte such as propylene carbonate, ethylene carbonate or diethyl carbonate) It means the percentage of the value obtained by dividing the mass of the wiped state (hereinafter also referred to as a test piece after immersion) by the mass of the test piece before immersion.

<Swelling ratio in electrolytic solution immersion>
The swelling ratio in immersion in the electrolytic solution is a swelling ratio evaluated using an organic solvent in which ethylene carbonate and diethyl carbonate are mixed in an equal volume, and is preferably 200% or more. In this study, evaluation was performed by the following method. Resin fine particles are dried to obtain a pre-immersion test piece of 2 cm × 2 cm × 1 mm. This is immersed in an organic solvent prepared by mixing ethylene carbonate and diethyl carbonate in equal volumes, and allowed to stand at 60 ° C. for 72 hours. The test piece is taken out from the organic solvent, and the organic solvent adhering to the surface is wiped off to obtain a test piece (hereinafter also referred to as a test piece after immersion).
A value obtained by dividing the mass of the test piece after immersion by the mass of the test piece after drying is defined as the swelling ratio in the electrolytic solution immersion. A resin having a small swelling rate does not absorb an electrolyte when used in a battery and inhibits lithium ion diffusion, resulting in a decrease in battery performance.

<Elution rate>
The dissolution rate is calculated by the following formula from the mass of each test piece (hereinafter, test piece after drying) obtained by drying the test piece before immersion and the test piece after immersion at 200 ° C. for 120 minutes.

Dissolution rate = [1- (Test piece mass after drying / Test piece mass before immersion)] × 100 (%)

<Elution rate in electrolytic solution immersion>
The elution rate in the electrolytic solution immersion is an elution rate evaluated using a mixture of ethylene carbonate and diethyl carbonate in an equal volume as an organic solvent, preferably 50% or less, more preferably 30% or less. In the case of a resin having a high elution rate, the inherent binding property of the binder cannot be maintained when used in an electrolytic solution, and the base layer may be peeled off, which may cause a problem of deterioration in the performance of the electricity storage device.

<Glass transition temperature>
The glass transition temperature (hereinafter also referred to as Tg) of the resin fine particles is preferably −60 to 60 ° C., and more preferably −20 to 40 ° C. In the case of −60 to 60 ° C., it is considered that the flexibility of the binder is moderate and excellent in adhesiveness, and that the resin fine particles are easy to maintain the shape, and the active material or a conductive carbon material is preferably coated. The glass transition temperature is a value obtained using a DSC (differential scanning calorimeter).

The measurement of the glass transition temperature by DSC (differential scanning calorimeter) can be performed as follows. About 2 mg of resin obtained by drying resin fine particles is weighed on an aluminum pan, the test container is set on a DSC measurement holder, and the endothermic peak of a chart obtained under a temperature rising condition of 10 ° C./min is read. The peak temperature at this time is defined as the glass transition temperature of the present invention.

<Average particle size>
The average particle diameter of the resin fine particles is preferably 50 to 500 nm. Moreover, it is preferable that the coarse particle having a particle diameter exceeding 1 μm is 5 parts by mass or less out of 100 parts by mass of the resin fine particles.
When the average particle diameter is 50 to 500 nm, the resin fine particles have an appropriate surface area with respect to the volume, and polar functional groups are effectively arranged on the particle surface. Excellent adhesion and particle stability. The number of coarse particles (resin fine particles having a particle diameter exceeding 1 μm) is preferably 5% or less of the total number of resin fine particles. In addition, the average particle diameter in this specification represents a volume average particle diameter, and is a value measured by a dynamic light scattering method. The particle size and number of coarse particles can be measured by a number counting method.

The average particle diameter can be measured by the dynamic light scattering method as follows. The resin fine particle dispersion is diluted with water so that the resin fine particle concentration becomes 0.035% by mass. About 5 ml of the diluted solution is injected into a cell of a measuring device [Microtrack manufactured by Nikkiso Co., Ltd.], and after measuring the refractive index conditions of the solvent (water in the present invention) and the resin according to the sample, the measurement is performed. The peak of the volume particle size distribution data (histogram) obtained at this time is defined as the average particle size of the present invention.

Measurement of the particle size and number of coarse particles by the number counting method is measured by, for example, “Accumizer 780” manufactured by Particle Sizing Systems, Inc., “Coulter Counter” manufactured by Coulter, etc. it can.

<Particle structure>
The resin fine particles of the present invention may have a multilayer structure in which the resin fine particles have a single composition or two or more different compositions.

<Usage of resin fine particles>
The resin fine particles of the present invention can be used as a binder used for a positive electrode or a negative electrode of a secondary battery. In addition, it can also be used for an electricity storage device, that is, a binder for an electrode such as a capacitor or a lithium ion capacitor, or a binder for a coating foil for an electrode underlayer.

<Composite ink>
The binder for an electricity storage device of the present invention includes an electrode active material, and if necessary, other resin fine particles, a water-soluble resin, a conductive material, a film forming aid, an antifoaming agent, a leveling agent, a preservative, and a pH adjuster. A compound ink can be manufactured by mix | blending additives, such as.

In the present invention, the resin fine particles are generally used in an amount of 0.1 to 20 parts by mass, preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the electrode active material. When the resin fine particles are usually 0.1 to 20 parts by mass, the power of binding the composite material layer and the current collector is excellent, the proportion of the resin fine particles in the composite material layer is small, the amount of energy that can be taken out is large, and the battery performance Excellent.

The active material for the electricity storage device is not particularly limited in material and shape, and an optimum material for various electricity storage devices can be appropriately selected.

The positive electrode active material for the lithium ion secondary battery is not particularly limited, but metal oxides capable of doping or intercalating lithium ions, metal compounds such as metal sulfides, and conductive polymers are used. be able to.

Examples thereof include transition metal oxides such as Fe, Co, Ni, and Mn, composite oxides with lithium, and inorganic compounds such as transition metal sulfides. Specifically, MnO, V ₂ O ₅ , V ₆ O ₁₃ ,
Transition metal oxide powders such as TiO _2, lithium nickelate with layered structure, lithium cobaltate, lithium manganate, composite oxide powder of lithium and transition metal such as spinel structure lithium manganate, phosphate compound with olivine structure Examples thereof include lithium iron phosphate materials, transition metal sulfide powders such as TiS ₂ and FeS.

In addition, conductive polymers such as polyaniline, polyacetylene, polypyrrole, and polythiophene can also be used. Moreover, you may mix and use said inorganic compound and organic compound.

The negative electrode active material for the lithium ion secondary battery is not particularly limited as long as it can be doped or intercalated with lithium ions. For example, metal oxides such as metal Li, alloys thereof such as tin alloys, silicon alloys, lead alloys, LiFe ₂ O ₃ , LiFe ₃ O ₄ , LiWO ₂ , lithium titanate, lithium vanadate, lithium silicon oxide, etc. Carbonaceous powder such as natural graphite, conductive carbon such as polyacetylene, poly-p-phenylene, amorphous carbonaceous material such as soft carbon and hard carbon, artificial graphite such as highly graphitized carbon material, or natural graphite And carbon-based materials such as carbon black, mesophase carbon black, resin-fired carbon material, vapor-grown carbon fiber, and carbon fiber. These negative electrode active materials can be used alone or in combination.

The size of these electrode active materials is preferably in the range of 0.05 to 100 μm, and more preferably in the range of 0.1 to 50 μm. And it is preferable that the dispersed particle diameter of the electrode active material (A) in compound-material ink is 0.5-20 micrometers. The dispersed particle size referred to here is a particle size (D50) at 50% by volume when the volume ratio of the particles is accumulated from a fine particle size distribution in the volume particle size distribution. For example, a dynamic light scattering type particle size distribution meter ("Microtrack UPA" manufactured by Nikkiso Co., Ltd.).

<Ink for forming the underlayer>
By blending the present invention or other resin fine particles, water-soluble resins, conductive materials, and additives such as film forming aids, antifoaming agents, leveling agents, preservatives, pH adjusters as necessary, An ink for forming a formation can be produced.

<Composite layer><Electric storage device electrode>
By applying the mixture ink to the current collector and drying, an electricity storage device electrode in which the mixture layer is formed on the current collector can be manufactured.

The material and shape of the current collector are not particularly limited, and an optimal material for various power storage devices can be appropriately selected.

For example, examples of the material for the current collector include metals and alloys such as aluminum, copper, nickel, titanium, and stainless steel. In the case of a lithium ion battery, aluminum is particularly preferable as the positive electrode material, and copper is preferable as the negative electrode material. In general, a flat foil is used as the shape, but a roughened surface, a perforated foil, or a mesh current collector can also be used.

Further, as the current collector, a current collector having a base layer obtained by applying a base layer forming ink to a metal foil and drying it can also be used. Accordingly, it is possible to suppress deterioration due to corrosion of the current collector and reduce resistance between the current collector and the composite material layer.

The method for coating the current collector with the ink for forming the underlayer or the composite ink is not particularly limited, and a known method can be used.

Specific examples include die coating method, dip coating method, roll coating method, doctor coating method, knife coating method, spray coating method, gravure coating method, screen printing method or electrostatic coating method, and the like. Examples of methods that can be used include standing drying, blower dryers, hot air dryers, infrared heaters, and far-infrared heaters, but are not particularly limited thereto.

<Power storage device>
By using the above electricity storage device electrode for at least one of the positive electrode and the negative electrode, an electricity storage device such as a secondary battery or a capacitor can be obtained.

Secondary batteries include lithium ion secondary batteries, sodium ion secondary batteries, magnesium ion secondary batteries, alkaline secondary batteries, lead storage batteries, sodium sulfur secondary batteries, lithium air secondary batteries, etc. An electrolyte solution, a separator, and the like that are conventionally known for each secondary battery can be appropriately used.
Examples of the capacitor include an electric double layer capacitor, a lithium ion capacitor, and the like, and an electrolyte, a separator, and the like that are conventionally known for each capacitor can be appropriately used.

(Electrolyte)
A case of a lithium ion secondary battery will be described as an example. As the electrolytic solution, an electrolyte containing lithium dissolved in a non-aqueous solvent is used.

As electrolytes, LiBF ₄ , LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , Li (CF ₃ SO ₂ ) ₃ C , LiI, LiBr, LiCl, LiAlCl, LiHF ₂ , LiSCN, or LiBPh _4, but are not limited thereto.

Although it does not specifically limit as a non-aqueous solvent, For example, carbonates, such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethylmethyl carbonate, and diethyl carbonate; γ-butyrolactone, γ-valerolactone, and γ- Lactones such as octanoic lactone; tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-methoxyethane, 1,2-ethoxyethane, and 1,2 -Glymes such as dibutoxyethane; esters such as methyl formate, methyl acetate, and methyl propionate; sulfoxides such as dimethyl sulfoxide and sulfolane; and nitriles such as acetonitrile. It is below. These solvents may be used alone or in combination of two or more.

Furthermore, the electrolyte solution may be a polymer electrolyte that is held in a polymer matrix and made into a gel. Examples of the polymer matrix include, but are not limited to, an acrylate resin having a polyalkylene oxide segment, a polyphosphazene resin having a polyalkylene oxide segment, and a polysiloxane having a polyalkylene oxide segment.

(separator)
Examples of the separator include, but are not limited to, a polyethylene nonwoven fabric, a polypropylene nonwoven fabric, a polyamide nonwoven fabric and those obtained by subjecting them to a hydrophilic treatment.

(Battery structure / configuration)
The structure of the lithium ion secondary battery, the electric double layer capacitor, and the lithium ion capacitor is not particularly limited, but is usually composed of a positive electrode and a negative electrode, and a separator provided as necessary. Paper type, cylindrical type, button type Various shapes can be formed according to the purpose of use, such as a laminated type.

EXAMPLES The present invention will be described more specifically with reference to the following examples. However, the following examples do not limit the scope of rights of the present invention. In Examples and Comparative Examples, “part” represents “part by mass”, and “%” represents “% by mass”.

(Measurement of glass transition temperature of resin fine particles)
It was measured by the method described in this specification.
(Measurement of average particle diameter of resin fine particles)
It was measured by the dynamic light scattering method described herein.
(Measurement of swelling rate of resin fine particles immersed in electrolyte)
It was measured by the method described in this specification.

<Preparation of aqueous dispersion of resin fine particles>
[Example 1]
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser was charged with 100 parts of ion exchange water and 0.2 part of Adeka Soap SR-10 (manufactured by ADEKA) as a surfactant, 30 parts of 4-hydroxybutyl acrylate, 0.5 parts of divinylbenzene, 8.5 parts of methyl methacrylate, 30 parts of butyl acrylate, 30 parts of styrene, 1 part of acrylic acid, 80 parts of ion-exchanged water, and ADEKA rear soap as a surfactant 1% of a pre-emulsion in which 1.8 parts of SR-10 (manufactured by ADEKA Corporation) had been mixed in advance was further added. After raising the internal temperature to 70 ° C. and sufficiently substituting with nitrogen, 10% of 10 parts of a 5% aqueous solution of potassium persulfate was added to initiate polymerization. After maintaining the inside of the reaction system at 70 ° C. for 5 minutes, the remaining pre-emulsion and the remaining 5% aqueous solution of potassium persulfate were dropped over 3 hours while maintaining the internal temperature at 70 ° C., and stirring was further continued for 2 hours. . After confirming that the conversion rate exceeded 98% by solid content measurement, the temperature was cooled to 30 ° C. The resin fine particles of Example 1 were obtained by adjusting the solid content to 30% with ion-exchanged water. In addition, solid content was calculated | required by 150 degreeC 20 minute baking residue.
The obtained resin fine particles had an average particle size of 150 nm and a glass transition temperature of −5 ° C.

[Examples 2 to 16, Comparative Examples 1 to 5]
Except having changed into the composition shown in Table 1, it synthesize | combined by the method similar to Example 1, and obtained the resin fine particle water dispersion of Examples 2-16 and Comparative Examples 1-2. In Comparative Examples 3 to 5, it was found that a large amount of aggregates adhered to the reaction vessel and the stirrer and synthesis was difficult. Table 1 shows the average particle diameter and glass transition temperature of the obtained resin fine particles.

[Explanation of monomer]
4HBA: 4-hydroxybutyl acrylate GLM: glycerol methacrylate HEMA: 2-hydroxyethyl acrylate AAM: acrylamide TBAA: Nt-butylacrylamide DEAA: diethylacrylamide MAAm: methacrylamide DVB: divinylbenzene EDMA: ethylene glycol dimethacrylate MMA: methyl methacrylate EA: ethyl acrylate BA: butyl acrylate 2EHA: 2-ethylhexyl acrylate CHMA: cyclohexyl methacrylate St: styrene AA: acrylic acid MAA: methacrylic acid adecalia soap SR-10: alkyl ether anionic surfactant (manufactured by ADEKA Corporation)
[Description of abbreviations]
Tg: glass transition temperature swelling ratio: electrolyte solution swelling ratio

[Example 17]
3,000 parts of lithium iron phosphate (LiFePO ₄ ) as a positive electrode active material, 167 parts of acetylene black, and carboxymethyl cellulose (Daicel Chemical Industries) as a thickener with respect to 100 parts of the solid content of the resin fine particles obtained in Example 1 CMC Daicel 1190) (200 parts) was added, and ion-exchanged water was added so that the solid composite material portion would be 52%, followed by kneading to prepare a lithium ion battery positive electrode composite ink. This was applied onto a 20 μm-thick aluminum foil serving as a current collector using a doctor blade so that the weight per unit area was 18 mg / cm ² , then dried by heating at 110 ° C. for 5 minutes, and then rolled by a roll press. The positive electrode for lithium ion secondary batteries of Example 17 having a thickness of 85 μm was prepared.
[Examples 18 to 32, Comparative Examples 6 to 7]
Except having used the resin particulate shown in Table 2, it carried out similarly to the lithium ion secondary battery positive electrode of Example 17, and produced the lithium ion secondary battery positive electrode of Examples 18-32 and Comparative Examples 6-7.
[Counter electrode 1 for evaluation]
Counter electrode for evaluation 1 in the same manner as the positive electrode of the lithium ion secondary battery of Example 17, except that polytetrafluoroethylene 30-J (Mitsui / Dupont Fluorochemical Co., Ltd., 60% aqueous dispersion) was used as the resin fine particles. Was made.
[Example 33]
3000 parts of artificial graphite as a negative electrode active material and 33 parts of carboxymethyl cellulose (CMC Daicel 1190, manufactured by Daicel Chemical Industries, Ltd.) as a thickener are added to 100 parts of the solid content of the resin fine particles of Example 1 to obtain a solid. Ion exchanged water was added so as to be 50%, and then kneaded to prepare a negative electrode mixture ink for a lithium ion battery. This was applied onto a copper foil having a thickness of 20 μm as a current collector using a doctor blade so that the weight per unit area was 9 mg / cm ^2, and then heat-dried at 110 ° C. for 5 minutes, followed by rolling by a roll press. Then, a negative electrode for a lithium ion secondary battery of Example 33 having a thickness of 70 μm was produced.
[Examples 34 to 48, Comparative Examples 8 to 9]
Lithium ion secondary battery negative electrodes of Examples 34 to 48 and Comparative Examples 8 to 9 were produced in the same manner as the lithium ion secondary battery negative electrode of Example 33 except that the resin fine particles shown in Table 2 were used.
[Counter electrode for evaluation 2]
A counter electrode for evaluation 2 was produced in the same manner as the negative electrode of the lithium ion secondary battery of Example 33 except that a styrene-butadiene latex 40% aqueous dispersion was used.

<Evaluation of adhesion>
Using a knife on the surface of each lithium ion secondary battery electrode, 10 incisions were made from the composite material layer to the depth reaching the current collector, vertically and horizontally at 1 mm intervals, and incisions were made. An adhesive tape was applied to the cut and immediately peeled off, and the degree of the active material falling off was determined by visual judgment. The evaluation criteria are shown below. The evaluation results are shown in Table 2.
A: “Peeling at 0 to 5 squares. Particularly excellent.”
○: “Peeling at 6 to 10 squares. No problem”
○ △: “Peeling at 11 to 20 squares. Usable level.”
Δ: “Peeling at 21 to 30 squares. There is a problem, but it can be used.”
×: “Peeling at 31 to 50 squares. Practical problem, unusable.”

<Coin-type lithium ion secondary battery for positive electrode evaluation>
The counter electrode 2 for evaluation was used as a counter electrode by punching out the positive electrode shown in Table 3 as a working electrode to a diameter of 16 mm. A separator (porous polypropylene film) inserted between the working electrode and the counter electrode, and electrolyte solution (mixed solvent in which ethylene carbonate and diethyl carbonate are mixed at a ratio of 1: 1 (volume ratio) at a concentration of 1M LiPF ₆ A coin-type battery was prepared. The coin type battery was formed in a glove box substituted with argon gas, and the following battery characteristic evaluation was performed after the coin type battery was produced.
<Coin-type lithium ion secondary battery for negative electrode evaluation>
A coin-type battery was produced in the same manner as the positive-electrode evaluation coin-type lithium ion secondary battery, except that the negative electrode shown in Table 4 was punched into a diameter of 16 mm as the working electrode and the counter electrode for evaluation 1 was used as the counter electrode. The following battery characteristic evaluation was performed.
(Charge / discharge cycle characteristics)
About the obtained coin-type battery, charging / discharging measurement was performed using the charging / discharging apparatus (SM-8 by Hokuto Denko).

After performing constant current and constant voltage charging (cutoff current 0.1 mA) at a charging current 1.0 mA at a charging current 1.0 mA, a constant current discharging is performed until a discharge final voltage 2.0 V is reached at a discharging current 1.0 mA. Went. These charge / discharge cycles are defined as one cycle, and 5 cycles of charge / discharge are repeated, and the discharge capacity at the fifth cycle is defined as the initial discharge capacity. (The initial discharge capacity is assumed to be 100% maintenance rate).

Next, after carrying out constant current and constant voltage charging (cutoff current 0.1 mA) at a charging end voltage of 4.0 V at a charging current of 1.0 mA in a 50 ° C. constant temperature bath, a discharge end voltage of 1.0 mA is discharged. Constant current discharge was performed until 2.0V was reached. This charge / discharge cycle was performed 200 times, and the percentage of the discharge capacity at the 200th cycle with respect to the initial discharge capacity was calculated as the discharge capacity maintenance ratio (the closer to 100%, the better).

A: “Discharge capacity maintenance ratio is 90% or more. Particularly excellent.”
○: “Discharge capacity maintenance rate is 85% or more and less than 90%. No problem at all”
○ △: “Discharge capacity maintenance rate is 80% or more and less than 85%. Usable level.”
Δ: “Discharge capacity maintenance rate is 75% or more and less than 80%.
×: “Discharge capacity maintenance rate is less than 75%.

As shown in Table 2, an electricity storage device electrode excellent in adhesion could be obtained by using the resin fine particles (Examples 1 to 16) of the present invention. Since the resin fine particles have polar functional groups and have an appropriate cross-linked structure, it is considered that high adhesion to the active material and the current collector was obtained.

As shown in Tables 3 and 4, it was found that by using the resin fine particles (Examples 1 to 16) of the present invention, an electrode having excellent battery characteristics and an electricity storage device using the same were obtained. This is presumably because the resin fine particles in the electrode can effectively maintain the binding between the active materials or between the active material and the current collector as a binder and suppress the deterioration of the electrode structure.

As shown to Tables 2-4, the electrical storage device electrode (Examples 17-19) using the resin microparticles (Examples 1-3, 5-10, 12-16) whose swelling rate in electrolyte solution immersion is 200% or more 21-26, 28-35, 37-42, 44-48), the electricity storage obtained using the resin fine particles (Examples 4 and 11) whose swelling ratio in the electrolyte immersion is 200% or less It turned out that the electrode which was excellent in the adhesiveness and battery characteristic compared with a device electrode (Example 20, 27, 36, 43) and an electrical storage device using the same were obtained. This is considered to be because, when the polarity of the resin increases the swelling rate, it has a favorable effect on the adhesion, and the ion diffusion has become advantageous by swelling with the electrolytic solution.

As shown in Tables 2 to 4, an electricity storage device using resin fine particles (Examples 1 to 3, 5, 7 to 10, 12, 13, 15 to 16) having a glass transition temperature of −60 to 60 ° C. Resins having a glass transition temperature higher than 60 ° C. by using electrodes (Examples 17 to 19, 21, 23 to 26, 28, 29, 31 to 35, 37, 39 to 42, 44, 45, 47 to 48) Electrode showing superior adhesion and battery characteristics compared with the electricity storage device electrode (Examples 22, 30, 38, 46) obtained using the fine particles (Examples 6 and 14), and an electricity storage device using the same It turns out that it is obtained. This is because the flexibility of the resin is appropriately controlled, so that the active materials in the electrodes or the binding between the active material and the current collector can be more effectively maintained, and the deterioration of the electrode structure can be suppressed. It is believed that there is.

As shown in Tables 2 to 4, an electricity storage device electrode using resin fine particles (Examples 1 to 3, 5, 8 to 10, 12, 13, 15 to 16) having an average particle size of 50 to 500 nm ( Examples 17 to 19, 21, 24 to 26, 28, 29, 31 to 35, 37, 40 to 42, 44, 45, 47 to 48) are resin fine particles having a larger average particle diameter (Example 7). It was found that excellent adhesion was exhibited as compared with the electricity storage device electrodes (Examples 23 and 39) obtained by use, and excellent battery characteristics as an electricity storage device. This is because an electrode structure that provides appropriate adhesion to constituent materials and an electrode structure that is effective for lithium ion conduction in a battery, etc., were obtained by appropriately controlling the average particle size of the resin. it is conceivable that.

As shown in Tables 2 to 4, a resin obtained by copolymerizing more than 40% by mass and less than 79.9% by mass of an alkyl (meth) acrylate monomer having 1 to 4 carbon atoms with respect to all monomers. Electric storage device electrodes (Examples 17 to 19, 21, 25, 26, 28, 29, 32 to 35, 37, 41) using fine particles (Examples 1 to 3, 5, 9 to 10, 12, 13, 16) , 42, 44, 45, and 48) are power storage device electrodes (Examples 24, 31, 40, and 47) using resin fine particles (Examples 8 and 15) obtained by copolymerizing compositions other than the above ratios. It was found that an electrical storage device having excellent adhesion as compared to) and an excellent battery characteristic can be obtained. This is presumably because the polymerization of the resin progressed uniformly, so that the polar functional group was uniformly present in the resin and effectively contributed to improving the adhesion.

Claims (7)

As constituent units of the resin fine particles, a monomer (a) unit having at least one functional group selected from the group consisting of a hydroxy group and an amide group, a crosslinkable monomer (b) unit, a monomer (a) and a monomer (b) A monomer (c) unit other than
The monomer (a) unit exceeds 20% by mass and is 50% by mass or less, the crosslinkable monomer (b) unit is 0.1% by mass to 10% by mass, and the monomer (c) ) Resin fine particles for an electricity storage device electrode, wherein the unit is 40% by mass or more and less than 79.9% by mass. The resin fine particle for an electricity storage device electrode according to claim 1, wherein the swelling ratio in immersion in the electrolytic solution is 200% or more. The resin fine particles for an electricity storage device electrode according to claim 1 or 2, wherein the resin fine particles have a glass transition temperature of -60 to 60 ° C. The resin fine particles for an electricity storage device electrode according to any one of claims 1 to 3, wherein the resin fine particles have an average particle size of 50 to 500 nm. As the monomer (c), the alkyl (meth) acrylate monomer (d) having 1 to 4 carbon atoms is contained in an amount of 40% by mass or more and less than 79.9% by mass with respect to all monomers constituting the resin fine particles. The resin fine particle for an electricity storage device electrode according to any one of claims 1 to 4. An electricity storage device electrode comprising the resin fine particles for an electricity storage device electrode according to any one of claims 1 to 5. An electricity storage device comprising a positive electrode, a negative electrode, and an electrolytic solution, wherein at least one of the positive electrode and the negative electrode is the electricity storage device electrode according to claim 6.